A silent chain, as disclosed in Japanese Patent No. 58-1304 (and corresponding U.S. Pat. No. 4,345,904), is often constructed such that a plurality of link plates are connected on a connecting pin in parallel with each other so as to be rotatable, a guide link is provided at an end portion of the connecting pin, a plate spring link is interposed at an appropriate position between adjacent parallel link plates, and/or a plate spring link is interposed between the guide and link plates.
This plate spring link is constructed like a leaf spring and functions to reduce clearance between the parallel link plates, to prevent a chord vibration of the chain from occurring, and to suppress generation of noises by creating resistance against bending movement of the chain. The plate spring link typically has a configuration as shown in FIG. 3 and is interposed between adjacent link plates or between the link plate and the adjacent guide plate. The typical configuration of this leaf-type spring plate, and its typical position between the plates of the silent chain, is illustrated in detail in aforesaid U.S. Pat. No. 4,345,904.
As shown in FIG. 3, a sprocket tooth T1 rotating in a direction of the arrow meshes with a link plate L1 of one link at its right end surface L', and a sprocket tooth T2 meshes with a link plate L2 of the next link, which link L2 is disposed at a leading side of the link plate L1, and is engaged at a right end surface L".
The link plates L1 and L2 are connected with each other in a longitudinal direction of the chain by a pair of connecting pins P1 and P2 which define a rocker-joint type. A plate spring link S is laid side by side and overlapped with the link plate L1. Link S has an insertion hole H for inserting the connecting pins P1 and P2. The inner diameter of the insertion hole H is designed to maintain play or clearance a with respect to the connecting pins P1 and P2. Both end surfaces S', S' of the plate spring link S are positioned inwardly of meshing surfaces L', L' of the link plate by a clearance b, and this clearance b is larger than the play a. That is, the clearance b is designed so as to maintain a relationship b&gt;a.
Such a relationship defined by a formula b&gt;a is a necessary condition to prevent both end surfaces S', S' of the plate spring link from protruding outwardly beyond the meshing surface L' of the link plate L1, even if the plate spring link S moves within the play a which is provided between the plate spring link S and the connecting pins. As a result, the end surfaces S', S' of the plate spring link can be prevented from interfering with the sprocket tooth T1, and therefore the plate spring link S is prevented from being broken.
Accordingly, in the above conventional structure, the manufacture of the plate spring link S must be carefully controlled for dimensions in order to satisfy the relationship that the dimension c of the plate spring link S with respect to the sprocket pitch circle PC and the dimension d of the link plate L1 correspond to the plate spring link S so as to provide the clearance 2b (i.e. 2b=d-c). Therefore, the stamping step of the plate spring link must be always carefully checked for manufacturing accuracy, and thus it is a troublesome process.
To resolve the above problem encountered in the prior art, the present invention provides a silent chain in which the portion of the plate spring link which projects into the sprocket pitch circle is cut out and removed in order to nullify a condition required against the relationship between the play a of the insertion hole and the clearance b of the plate spring link with respect to a meshing surface of a link plate. The plate spring link has a substantially X-shaped configuration by cutting out a part of the insertion hole for the connecting pins, or has a configuration of a glasses frame.
Accordingly, since a plate spring link in accordance with the present invention does not have an extending portion which extends into the sprocket pitch circle, the plate spring link does not protrude beyond the meshing surface of the link plate. Therefore, the plate spring link does not interfere with a sprocket tooth.
Moreover, in the case that the external configuration of the plate spring link is formed of substantially an X-shaped configuration by providing an opened concave portion at each end of the plate spring link, it is not necessary to carry out a separate stamping step for making an insertion hole for the connecting pin. The gripping recess portion for gripping the connecting pin is formed at the same time as stamping the external configuration. Further, it can be prevented that the plate spring link is removed from the connecting pin. Furthermore, in the case that the plate spring link is formed in the shape of a glasses frame, the plate spring link is prevented from being partly lost even when a crack occurs on the periphery of the insertion hole.